腐殖质生理活性及其与化学组成关系的研究进展

Progress on the physiological activity of humic substances and correlation with its chemical composition

腐殖质(HS)是生物体外具备生物学活性的最稳定有机物形式之一。本文综述了HS的化学组成、结构特征和生理活性,依据HS化学组成、结构特征和生理活性的相互关系探讨了HS具有生理活性的内在机制。HS化学组成具有不确定性,超分子结构假设目前被普遍接受。HS通过促进根毛形成和侧根发育、激活质膜H+-ATP酶产生有利的电化学梯度以及自身酸性官能团的螯合作用等促进植物对矿质元素的吸收利用;HS具有类激素活性,植物根际促生细菌(PGPR)分泌物或HS自体组分吲哚-3-乙酸(IAA)能够激活细胞质膜H+-ATPase,HS还能够增加内源植物激素水平,促进植物生长发育;HS通过介导信使NO激活细胞质膜H+-ATPase,清除HS与细胞作用产生的活性氧(ROS),HS通过NO和抗氧化酶调节细胞内ROS稳态,介导根系发育和形态结构。本文还着重探讨了HS生理活性与化学组成的相关性,其中官能团—COOH和—OH活性位点的作用、醌基的电子传递,以及HS亲水疏水平衡与HS生理活性密切相关。未来HS研究工作的重点在于深入研究HS分子结构、明确具备生理活性的“共性结构原件”、阐明HS诱导胞内信号传导通路之间的交叉反馈机制、揭示HS对细胞内物质和能量代谢相关基因表达的调节机制。

Humic substances(HS)are one of the most stable forms of organic matter with in vitro biological activity.This study reviews the chemical composition,structural characteristics,and physiological activity of HS and discusses the internal mechanism of the physiological activity based on the relationship between these aspects.The chemical composition of HS is uncertain,and the supramolecular structure model of HS is currently generally accepted.HS promotes the absorption and utilization of mineral elements by promoting the formation of root hairs and lateral root development,activating plasma membrane H+-ATPase to generate favorable electrochemical gradients and chelating mineral elements with acidic functional groups.With hormone-like activity,HS IAA secreted by plant rhizosphere growth promoting bacteria(PGPR)or HS autologous component can activate plasma membrane H+-ATPase.HS can also increase endogenous plant hormone levels and promote plant growth and development.HS activates plasma membrane H+-ATPase by mediating messenger NO to eliminate reactive oxygen species(ROS)generated from HS-affected cells.HS mediates root development and morphological structure by regulating intracellular ROS homeostasis through NO and antioxidant enzymes.This study additionally focuses on the correlation between HS physiological activity and its chemical composition;the role of active sites such as-COOH and-OH,the electron transfers of quinone groups,and HS hydrophilic-hydrophobic balance are closely related to HS physiological activities.Future HS research should focus on analyzing HS molecular structures,clarifying the“common structural element”with physiological activity of the cross-feedback mechanism between HS-induced intracellular signal transduction pathways,and revealing the regulation mechanism of HS on gene expression related to material and energy metabolism in cells,aiming to provide a theoretical basis for the in-depth study of HS physiological activity mechanism and agricultural applications.